AP Stats Review
Use Scenario 6-6. The probability that X = 1.5 is a. 0. c. 1/4. e. 1/2. b. very small; slightly larger than 0. d. 1/3.
a. 0.
7. Birthweights at a local hospital have a Normal distribution with a mean of 110 oz. and a standard deviation of 15 oz. Which of the following is the proportion of infants with birthweights between 125 oz. and 140 oz.?
a. 0.135
57. Use Scenario 6-12. Which of the following expresses the probability that the student gets no questions correct?
b. (0.75)2
88. The essential difference between an experiment and an observational study is that a. observational studies may have confounded variables, but experiments never do. b. in an experiment, people must give their informed consent before being allowed to participate. c. observational studies are always biased. d. observational studies cannot have response variables. e. an experiment imposes treatments on the subjects, but an observational study does not.
e. an experiment imposes treatments on the subjects, but an observational study does not.
The probability of a randomly selected adult having a rare disease for which a diagnostic test has been developed is 0.001. The diagnostic test is not perfect. The probability the test will be positive (indicating that the person has the disease) is 0.99 for a person with the disease and 0.02 for a person without the disease. ____ 48. Use Scenario 5-7. If a randomly selected person is tested and the result is positive, the probability the individual has the disease is a. 0.001. b. 0.019. c. 0.020. d. 0.021. e. 0.047.
d. 0.021
The following table compares the hand dominance of 200 Canadian high-school students and what methods they prefer using to communicate with their friends. Use Scenario 5-11. What is the probability that the student chosen is left-handed or prefers to communicate with friends in person? a. 0.065 b. 0.17 c. 0.425 d. 0.53 e. 0.595
d. 0.53
Use Scenario 6-14. In a production run of 800 bottles, what is the standard deviation for the number of bottles with improperly applied caps? a. 1.38 b. 6.16 c. 6.32 d. 6.89 e. 8.72
b. 6.16
The bar graph below summarizes responses of dog owners to the question, "Where in the car do you let your dog ride?" Which of the following statements is true?
d. The vertical scale of this graph exaggerates the difference between the percentage who let their dogs ride in the driver's lap versus a passenger's lap.
Use Figure 2-1. For this density curve, which of the following is true?
e. All of the above.
The distribution of household incomes in a small town is strongly skewed to the right. The mean income is $42,000 and the standard deviation is $24,000. The Ames family's household income is $60,000. The z-score for the Ames family's income is a. -0.75 d. 0.86 b. 0.3 e. None of these, because z-score cannot be used unless the distribution is Normal. c. 0.75
c. 0.75
In a particular game, a fair die is tossed. If the number of spots showing is either four or five, you score 1 point. If the number of spots showing is six, you score 4 points. And if the number of spots showing is one, two, or three, you score 0. You are going to play the game twice. ____ 44. Use Scenario 5-4. The probability that you score at least 1 point both times is a. 1/36. b. 4/36. c. 1/4. d. 1/2. e. 3/4
c. 1/4.
Consider the following cumulative relative frequency graph of the scores of students in an introductory statistics course: A grade of C or C+ is assigned to a student who scores between 55 and 70. The percentage of students who obtained a grade of C or C+ is a. 15% b. 20% c. 25% d. 30% e. 50%
c. 25%
Which of the following is not a major principle of good design for all experiments? a. Comparison to a control. b. Replication c. Blocking d. Randomization e. All of these are important principles for every experiment.
c. Blocking
54. Which of the following statements about influential points and outliers are true? I. An influential point always has a high residual. II. Outliers are always influential points. III. Removing an influential point always causes a marked change in either the correlation, the regression equation, or both. a. I only. c. III only. e. I, II, and III are all true. b. II only. d. II and III only
c. III only.
At a school with 600 students, 25% of them walk to school each day. If we choose a random sample of 40 students from the school, is it appropriate to model the number of students in our sample who walk to school with a binomial distribution where n = 40 and p = 0.25? a. No, the appropriate model is a geometric distribution with n = 40 and p = 0.25. b. No, it is never appropriate to use a binomial setting when we are sampling without replacement. c. Yes, because the sample size is less than 10% of the population size. d. Yes, because and n < 30. e. We can't determine whether a binomial distribution is appropriate unless the number of trials is known.
c. Yes, because the sample size is less than 10% of the population size.
Use Scenario 1-7. The median birth weight is approximately a. 80.5 ounces. b. 90 ounces. c. 100 ounces. d. 110 ounces. e. 120 ounces
d. 110 ounces.
For a physics course containing 10 students, the maximum point total for the quarter was 200. The point totals for the 10 students are given in the stemplot below. 11 6 8 12 1 4 8 13 3 7 14 2 6 15 16 17 9 ____ 67. Use Scenario 1-4. To which of the following data sets does this stemplot correspond? a. All integers between 116 and 179 b. 1, 2, 3, 4, 6, 6, 7, 8, 8, 9 c. 16, 18, 21, 24, 28, 33, 37, 42, 46, 79 d. 116, 118, 121, 124, 128, 133, 137, 142, 146, 179 e. None of these
d. 116, 118, 121, 124, 128, 133, 137, 142, 146, 179
Suppose that 40% of the cars in a certain town are white. A person stands at an intersection waiting for a white car. Let X = the number of cars that must drive by until a white one drives by. ____ 29. Use Scenario 6-15. The expected value of X is: a. 1 b. 1.5 c. 2 d. 2.5 e. 3
d. 2.5
A small store keeps track of the number X of customers that make a purchase during the first hour that the store is open each day. Based on the records, X has the following probability distribution. X 0 1 2 3 4 P(X) 0.1 0.1 0.1 0.1 0.6 ____ 65. Use Scenario 6-5. Use The mean number of customers that make a purchase during the first hour that the store is open is a. 2.0. b. 2.5. c. 2.9. d. 3.0. e. 4.0.
d. 3.0.
55. Use Scenario 3-7. If we were to use this least-squares regression line to predict the protein content of another bean variety on the basis of calorie content, which of the following values from the computer output describes the expected average error in our prediction? a. 0.02409 b. 0.432 c. 0.432 d. 3.37648 e. 15.93
d. 3.37648
73. A company produces packets of soap powder that are labeled "Giant Size 32 Ounces." The actual weight of soap powder in a box has a Normal distribution with a mean of 33 oz. and a standard deviation of 0.7 oz. 95% of packets actually contain more than x oz. of soap powder. What is x? a. 31.60 b. 31.85 c. 32.88 d. 34.15 e. 34.40
d. 34.15
A jar has 250 marbles in it, 40 of which are red. What is the largest sample size we can take from the jar (without replacement) if we want to use the binomial distribution to model the number of red marbles in our sample? a. 50 c. 25 e. You can't use a binomial distribution in this setting. b. 40 d. 4
d. 4
Below is a histogram of the heights of gold-medal-winning high jumps in the Olympic Games since 1896. ____ 83. Use Scenario 1-3. Based on this histogram, the percentage of the winning jumps that were at least 80 inches is about a. 10%. b. 35%. c. 45%. d. 55%. e. 90%.
d. 55%.
An assignment of probabilities must obey which of the following? a. The probability of any event must be a number between 0 and 1, inclusive. b. The sum of all the probabilities of all outcomes in the sample space must be exactly 1. c. The probability of an event is the sum of the probabilities of outcomes in the sample space in which the event occurs. d. All three of the above. e. A and B only.
d. All three of the above.
Use Scenario 1-1. Your percentage of the proportion of males that are registered as Democrats is part of a. The marginal distribution of political party registration. b. The marginal distribution of gender. c. The conditional distribution of gender among Democrats. d. The conditional distribution of political party registration among males. e. The conditional distribution of males within gender.
d. The conditional distribution of political party registration among males.
The histogram below shows the distribution of heights for 100 randomly selected school children in Great Britain.
Roughly symmetric, centered at about 150, range 80.
Scenario 5-8 A student is chosen at random from the River City High School student body, and the following events are recorded: M = The student is male F = The student is female B = The student ate breakfast that morning. N = The student did not eat breakfast that morning. The following tree diagram gives probabilities associated with these events.
a. 0.32
Sulé's job is just a few bus stops away from his house. While it can be faster to take the bus to work, it's more variable, because of variations in traffic. He estimates that the commute time to work by bus is approximately Normally distributed with a mean of 12 minutes and a standard deviation of 4 minutes. The commute time if he walks to work is also approximately Normally distributed with a mean of 16 minutes with a standard deviation of 1 minute. What is the probability that the bus will be faster than walking? a. 0.8340 b. 0.8485 c. 0.8980 d. 0.9756 e. 0.9896
a. 0.8340
A poll shows that 60% of the adults in a large town are registered Democrats. A newspaper reporter wants to interview a local democrat regarding a recent decision by the City Council. ____ 43. Use Scenario 6-16. If the reporter asks adults on the street at random, what is the probability that he will find a Democrat by the time he has stopped three people? a. 0.936 b. 0.216 c. 0.144 d. 0.096 e. 0.064
a. 0.936
2. IQs among undergraduates at Mountain Tech are approximately Normally distributed. The mean undergraduate IQ is 110. About 95% of undergraduates have IQs between 100 and 120. The standard deviation of these IQs is about a. 5. b. 10. c. 15. d. 20. e. 25
a. 5.
80. A soft-drink machine can be regulated so that it discharges an average of oz. per cup. If the ounces of fill are Normally distributed with a standard deviation of 0.4 oz., what value should be set at so that 98% of 6-oz. cups will not overflow? a. 5.18 b. 6.00 c. 6.18 d. 6.60 e. 6.82
a. 5.18
Use Scenario 3-3. If another data point were added with an air temperature of 0º C and a stopping distance of 80 feet, the correlation would a. Decrease, since this new point is an outlier that does not follow the pattern in the data. b. Increase, since this new point is an outlier that does not follow the pattern in the data. c. Stay nearly the same, since correlation is resistant to outliers. d. Increase, since there would be more data points. e. Whether this data point causes an increase or decrease cannot be determined without recalculating the correlation.
a. Decrease, since this new point is an outlier that does not follow the pattern in the data.
Suppose each employee in the company receives a $3,000 raise for next year (each employee's salary is increased by $3,000). ____ 28. Use Scenario 2-1. The interquartile range of the salaries for the employees will a. be unchanged. c. be multiplied by $3,000. e. decrease by $3,000. b. increase by $3,000. d. increase by square root $3,000
a. be unchanged.
Ignoring twins and other multiple births, assume that babies born at a hospital are independent random events with the probability that a baby is a boy and the probability that a baby is a girl both equal to 0.5. ____ 91. Use Scenario 5-3. The events A = the next two babies are boys, and B = the next two babies are girls are a. disjoint. b. conditional. c. independent. d. complementary e. none of the above.
a. disjoint.
49. The principle reason for the use of controls in designing experiments is that it a. distinguishes a treatment effect from the effects of confounding variables. b. allows double-blinding. c. reduces sampling variability. d. creates approximately equal groups for comparison. e. eliminates the placebo effect.
a. distinguishes a treatment effect from the effects of confounding variables.
Consider the following scatterplot of amounts of CO (carbon monoxide) and NOX (nitrogen oxide) in grams per mile driven in the exhausts of cars. The least-squares regression line has been drawn in the plot. 6. Use Scenario 3-4. In the scatterplot, the point indicated by the open circle
a. has a negative value for the residual.
____ 66. Suppose there are three balls in a box. On one of the balls is the number 1, on another is the number 2, and on the third is the number 3. You select two balls at random and without replacement from the box and note the two numbers observed. The sample space S consists of the three equally likely outcomes {(1, 2), (1, 3), (2, 3)}. Let X be the sum of the numbers on two balls selected. Which of the following is the correct probability distribution for X? a. c. e. b. d
b
You are stuck at the Vince Lombardi rest stop on the New Jersey Turnpike with a dead battery. To get on the road again, you need to find someone with jumper cables that connect the batteries of two cars together so you can start your car again. Suppose that 16% of drivers in New Jersey carry jumper cables in their trunk. You begin to ask random people getting out of their cars if they have jumper cables. Use Scenario 6-17. You're going to give up and call a tow truck if you don't find jumper cables by the time you've asked 10 people. What's the probability you end up calling a tow truck?
b. 0.1749
A worn out bottling machine does not properly apply caps to 5% of the bottles it fills. ____ 60. Use Scenario 6-14. If you randomly select 20 bottles from those produced by this machine, what is the approximate probability that exactly 2 caps have been improperly applied? a. 0.0002 b. 0.19 c. 0.74 d. 0.81 e. 0.92
b. 0.19
In a certain population of students, the number of calculators a student owns is a random variable X described by the following probability distribution: X 0 1 2 P(X) 0.2 0.6 0.2 ____ 71. Use Scenario 6-3. Which of the following is the standard deviation of X? a. 1 b. 0.6325 c. 0.4472 d. 0.4 e. The answer cannot be computed from the information given.
b. 0.6325
Use Scenario 6-6. The probability that X is at least 1.5 is a. 0. b. 1/4. c. 1/3. d. 1/2. e. 3/4.
b. 1/4
All of the following distributions have a mean of 10. Which has the largest standard deviation? a. 5, 5, 5, 10, 10, 10, 15, 15, 15 b. 5, 5, 5, 15, 15, 15 d. 10, 10, 10, 10, 10, 10, 10, 10 e. 5, 8, 10, 12, 15 c. 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15
b. 5, 5, 5, 15, 15, 15
13. Which of the following statements is true? a. In a distribution that is skewed right, the median is larger than the mean. b. Fifty percent of the scores in a distribution are between the first and third quartile. c. The third quartile of a distribution is always greater than the mean. d. The median of a distribution is always greater than the mean. e. The range of a distribution is typically smaller than the interquartile range.
b. Fifty percent of the scores in a distribution are between the first and third quartile.
64. A poker player is dealt poor hands for several hours. He decides to bet heavily on the last hand of the evening on the grounds that after many bad hands he is due for a winner. a. He's right, because the winnings have to average out. b. He's wrong, because successive deals are independent of each other. c. He's right, because successive deals are independent of each other. d. He's wrong, because he's clearly on a "cold streak." e. Whether he's right or wrong depends on how many bad hands he's been dealt so far
b. He's wrong, because successive deals are independent of each other.
Which of the following best describes the correlation r? a. The average of the products of each of the X and Y values for each point b. The average of the products of the standardized scores of X and Y for each point. c. The average of the squared products of the standardized scores of X and Y for each point. d. The average of the differences between each X value and each Y value. e. The average perpendicular distance between each data point and the least-squares regression line.
b. The average of the products of the standardized scores of X and Y for each point.
A local tax reform group polls the residents of the school district and asks the question, "Do you think the school board should stop spending taxpayers' money on non-essential arts programs in elementary schools?" The results of this poll are likely to a. Underestimate support for arts programs because of undercoverage. b. Underestimate support for arts programs because of the way the question is worded. c. Overestimate support for arts programs because of undercoverage. d. Overestimate support for arts programs because of the way the question is worded. e. Accurately estimate support for arts programs
b. Underestimate support for arts programs because of the way the question is worded
The most important advantage of experiments over observational studies is that a. experiments are usually easier to carry out. b. experiments can give better evidence of causation. c. confounding cannot happen in experiments. d. an observational study cannot have a response variable. e. observational studies cannot use random samples.
b. experiments can give better evidence of causation.
Twelve people who suffer from chronic fatigue syndrome volunteer to take part in an experiment to see if shark fin extract will increase one's energy level. Eight of the volunteers are men, and four are women. Half of the volunteers are to be given shark fin extract twice a day, and the other half are to be given a placebo twice a day. We wish to make sure that four men and two women are assigned to each of the treatments, so we decide to use a block design with the men forming one block and the women the other. A block design is appropriate in this experiment if a. we want to be able to compare effects on energy level in men and women. b. we believe men and women will respond differently to treatments. c. gender equity is an important legal consideration in this study. d. we want the conclusions to apply equally to men and women. e. all of the above.
b. we believe men and women will respond differently to treatments.
You are playing a board game with some friends that involves rolling two six-sided dice. For eight consecutive rolls, the sum on the dice is 6. Which of the following statements is true? a. Each time you roll another 6, the probability of getting yet another 6 on the next roll goes down. b. Each time you roll another 6, the probability of getting yet another 6 on the next roll goes up. c. You should find another set of dice: eight consecutive 6's is impossible with fair dice. d. The probability of rolling a 6 on the ninth roll is the same as it was on the first roll. e. None of these statements is true
d. The probability of rolling a 6 on the ninth roll is the same as it was on the first roll.
Which of the following is not a random variable? a. The number of heads in ten tosses of a fair coin. b. The number of passengers in cars passing though a toll booth. c. The age of the driver in cars passing through a toll booth. d. The response of randomly-selected people to the question, "What is your favorite TV sit-com?" e. The response of randomly-selected people to the question, "How many hours of sleep did you get last night?
d. The response of randomly-selected people to the question, "What is your favorite TV sit-com?"
18. An ecologist studying starfish populations collects the following data on randomly-selected 1-meter by 1-meter plots on a rocky coastline. --The number of starfish in the plot. --The total weight of starfish in the plot. --The percentage of area in the plot that is covered by barnacles (a popular food for starfish). --Whether or not the plot is underwater midway between high and low tide. How many of these measurements can be treated as continuous random variables and how many as discrete random variables? a. Three continuous, one discrete. b. Two continuous, two discrete. c. One continuous, three discrete. d. Two continuous, one discrete, and a fourth that cannot be treated as a random variable. e. One continuous, two discrete, and a fourth that cannot be treated as a random variable.
d. Two continuous, one discrete, and a fourth that cannot be treated as a random variable.
52. A stack of four cards contains two red cards and two black cards. I select two cards, one at a time, and do not replace the first card selected before selecting the second card. Consider the events A = the first card selected is red B = the second card selected is red The events A and B are a. independent and disjoint. b. not independent, but disjoint. c. independent, not disjoint d. not independent, not disjoint. e. independent, but we can't tell if they are disjoint without further information.
d. not independent, not disjoint.
In probability and statistics, a random phenomenon is a. something that is completely unexpected or surprising b. something that has a limited set of outcomes, but when each outcome occurs iscompletely unpredictable. c. something that appears unpredictable, but each individual outcome can be accurately predicted with appropriate mathematical or computer modeling. d. something that is unpredictable from one occurrence to the next, but over the course of many occurrences follows a predictable pattern e. something whose outcome defies description.
d. something that is unpredictable from one occurrence to the next, but over the course of many occurrences follows a predictable pattern
The following is a boxplot of the birth weights (in ounces) of a sample of 160 infants born in a local hospital. ____ 45. Use Scenario 1-7. The number of children with birth weights between 102 and 122 ounces is approximately: a. 20. b. 40. c. 50. d. 80. e. 100.
d.80
A basketball player makes 75% of his free throws. We want to estimate the probability that he makes 4 or more frees throws out of 5 attempts (we assume the shots are independent). To do this, we use the digits 1, 2,and 3 to correspond to making the free throw and the digit 4 to correspond to missing the free throw. If thetable of random digits begins with the digits below, how many free throw does he hit in our first simulation of five shots? a. 1 b. 2 c. 3 d. 4 e. 5
e. 5
An ecologist who was studying starfish populations collected starfish of the species Pisaster was interested in the distribution of sizes of starfish on a certain shoreline. One measure of size is "arm length." Below is a cumulative relative frequency distribution for the arm length of 102 Pisaster individuals. The median and interquartile range of this distribution are approximately: a. Median is 15.2; Intequartile range is 12.5 to 16.2 b. Median is 13; Interquartile range is 13 to 16.1 c. Median is 13; Interquartile range is 3.1 d. Median is 13; Intequartile range is 3.7 e. Median is 15.2; Intequartile range is 3.7
e. Median is 15.2; Intequartile range is 3.7
95. Use Scenario 3-2. The wine consumption data are in liters of alcohol per person. Which of these are all measured in liters of alcohol per person? a. The mean, the first quartile, and the variance of wine consumption. b. The median wine consumption and the correlation between wine consumption and heart disease deaths. c. The median, the variance, and the standard deviation of wine consumption. d. The standard deviation of wine consumption and the correlation between wine consumption and heart disease deaths. e. The mean, the median, and the standard deviation of wine consumption.
e. The mean, the median, and the standard deviation of wine consumption.
68. Use Scenario 4-6. Suppose half of the 8:30 students are randomly allocated to the treatment group (two cups of coffee), the other half to the control group (two cups of decaf). In addition, half of the 9:30 students are randomly allocated to the treatment group, the other half to the control group. This is an example of a a. voluntary response study. b. stratified sampling procedure. c. matched pairs design. d. completely randomized design. e. randomized block design.
e. randomized block design.
You measure the age, marital status and earned income of an SRS of 1463 women. The number and type of variables you have measured is a. four; one categorical and two quantitative, and one individual. b. four; two categorical and two quantitative. c. four; one categorical and three quantitative. d. three; two categorical and one quantitative. e. three; one categorical and two quantitative
e. three; one categorical and two quantitative
Use Scenario 5-11. Which of the following statements supports the conclusion that the event "Right-handed" and the event "Online" are not independent?
E
The weights of grapefruits of a certain variety are approximately Normally distributed with a mean of 1 pound and a standard deviation of 0.12 pounds. ____ 59. Use Scenario 6-9. Which of the following is closest to the probability that a randomly-selected grapefruit weights more than 1.25 pounds? a. 0.0188 b. 0.0156 c. 0.3156 d. 0.4013 e. 0.5987
a. 0.0188
Scenario 1-2 Use Scenario 1-2. The percent of cars with 4-cylinder engines that are made in Germany is a. 10.5%. b. 21%. c. 50%. d. 80%. e. 91%.
a. 10.5%
Scenario 6-1 Flip a coin four times. If Z = the number of heads in four flips, then the probability distribution of Z is given in the table below. Z 0 1 2 3 4 P(Z) 0.0625 0.2500 0.3750 0.2500 0.0625 ____ 8. Use Scenario 6-1. An expression the represents the probability of at least one tail is
b. P(Z _< 3).
I select two cards from a deck of 52 cards and observe the color of each (26 cards in the deck are red and 26 are black). Which of the following is an appropriate sample space S for the possible outcomes? a. S = {red, black} b. S = {(red, red), (red, black), (black, red), (black, black)}, where, for example, (red, red) stands for the event "the first card is red and the second card is red." c. S = {(red, red), (red, black), (black, black)}, where, for example, (red, red) stands for the event "the first card is red and the second card is red." d. S = {0, 1, 2}. e. All of the above.
b. S = {(red, red), (red, black), (black, red), (black, black)}, where, for example, (red, red) stands for the event "the first card is red and the second card is red."
76. Use Scenario 3-3. The correlation between temperature and stopping distance a. is approximately 0.9. b. is approximately 0.6. c. is approximately 0.0. d. is approximately -0.6. e. cannot be calculated, because some of the x values are negative
b. is approximately 0.6.
There are three children in a room, ages three, four, and five. If another four-year-old child enters the room the a. mean age will stay the same but the variance will increase. b. mean age will stay the same but the variance will decrease. c. mean age and variance will stay the same. d. mean age and variance will increase. e. mean age and variance will decrease.
b. mean age will stay the same but the variance will decrease.
The Normal curve below describes the death rates from heart disease per 100,000 people in developed countries in the 1990's. The mean and standard deviation of this distribution are approximately a. Mean 100; Standard Deviation 65 d. Mean 190; Standard Deviation 100 b. Mean 100; Standard Deviation 100 e. Mean 200; Standard Deviation 130 c. Mean 190; Standard Deviation 65
c. Mean 190; Standard Deviation 65
86. There is a positive correlation between the size of a hospital (measured by number of beds) and the median number of days that patients remain in the hospital. Does this mean that you can shorten a hospital stay by choosing to go to a small hospital? a. No - a negative correlation would allow that conclusion, but this correlation is positive. b. Yes - the correlation establishes that hospital size is the reason for shorter stays. c. No - the positive correlation is probably explained by the fact that seriously ill people go to large hospitals d. Yes - but only if r is greater than 0.5. e. Yes - but only if r is very close to 1.
c. No - the positive correlation is probably explained by the fact that seriously ill people go to large hospitals
A stratified random sample is appropriate when a. It is impractical to take a simple random sample because the population is too large. b. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is quite different within the groups but very similar between groups. c. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups. d. You intend to take a sample of more than 100 individuals. e. You want to avoid undercoverage of certain groups
c. The population can be easily subdivided into groups according to some categorical variable, and the variable you are measuring is very similar within the groups but quite different between groups.
90. One way economists measure the health of the real estate market is by counting "housing starts," or the number of permits issued for construction of new homes. Below is a graph displaying housing starts (in thousands) in the United States from 2006 to 2009. What is the principle weakness of this graphical presentation of data? a. The "thousands" label on the vertical scale is confusing and misleading. b. The data only shows housing starts for four years, which is not enough time to identify a meaningful trend. c. Using proportionally-sized pictograms exaggerates the difference between years. d. Data of this type should only be displayed in a pie chart. e. It is unclear which dimension of the house represents the number of housing starts for that year.
c. Using proportionally-sized pictograms exaggerates the difference between years.
85. A simple random sample is a. any sample selected by using chance. b. any sample that gives every individual the same chance to be selected. c. a sample that gives every possible sample of the same size the same chance to be selected. d. a sample that selects equal numbers of individuals from each stratum. e. a sample that contains the same percent of each subgroup in the population.
c. a sample that gives every possible sample of the same size the same chance to be selected.
84. A stemplot of a set of data is roughly symmetric, but the data do not even approximately follow the 68-95-99.7 rule. We conclude that the data are a. Normal, but not Standard Normal. b. Standard Normal. c. not Normal. d. Normal. e. skewed in both directions.
c. not Normal
2. The principle reason for replication in designing experiments is that it a. distinguishes a treatment effect from the effects of other, possibly confounding variables. b. allows double-blinding. c. reduces sampling variability. d. creates approximately equal groups for comparison. e. eliminates the placebo effect.
c. reduces sampling variability
A score's percentile is a measure of a. center c. relative location e. relative frequency b. spread d. skew
c. relative location
The mp3 music files on Sharon's computer have a mean size of 4.0 megabytes and a standard deviation of 1.8 megabytes. She wants to create a mix of 10 of the songs for a friend. Let the random variable T = the total size (in megabytes) for 10 randomly selected songs from Sharon's computer. ____ 74. Use Scenario 6-11. What is the standard deviation of T? (Assume the lengths of songs are independent.) a. 1.80 b. 3.24 c. 5.69 The mp3 music files on Sharon's computer have a mean size of 4.0 megabytes and a standard deviation of 1.8 megabytes. She wants to create a mix of 10 of the songs for a friend. Let the random variable T = the total size (in megabytes) for 10 randomly selected songs from Sharon's computer. ____ 74. Use Scenario 6-11. What is the standard deviation of T? (Assume the lengths of songs are independent.) a. 1.80 b. 3.24 c. 5.69 d. 18.00 e. 32.40
d. 18.00
Mr. Williams asked the 26 seniors in his statistics class how many A.P. courses they had taken during high school. Below is a dot plot summarizing the results of his survey. Use Scenario 1-5. The interquartile range for the number of A.P. Courses is a. 3 to 4 b. 2.5 to 5 c. 3 to 5 d. 2 e. 2.5
d. 2
87. Which of the following is true about every random variable I. It takes on numerical or categorical values. II. It describes the results of a random phenomenon. III. Its behavior can be described by a probability distribution. a. I only b. II only c. III only d. II and III e. All three statements are true
d. II and III
Use Scenario 4-3. Which of the following statements is true? a. If we use another list of random digits to select the sample, we would get the same result as that obtained with the list actually used. b. If we use another list of random digits to select the sample, we would get a completely different sample than that obtained with the list actually used. c. If we use another list of random digits to select the sample, we would get, at most, one name in common with that obtained with the list actually used. d. If we use another list of random digits to select the sample, the result obtained with the list actually used would be just as likely to be selected as any other set of three names. e. If we use another list of random digits to select the sample, the result obtained with the list actually used would be far less likely to be selected than any other set of three names.
d. If we use another list of random digits to select the sample, the result obtained with the list actually used would be just as likely to be selected as any other set of three names.
Suppose that scores on a certain IQ test are Normally distributed with mean 110 and standard deviation 15.Then about 40% of the scores are between a. 80 and 140. c. 106 and 110. e. 102 and 118. b. 65 and 155. d. the 25th and 75th percentiles.
e. 102 and 118
69. Each day, Mr. Bayona chooses a one-digit number from a random number table to decide if he will walk towork or drive that day. The numbers 0 through 3 indicate he will drive, 4 through 9 mean he will walk. Ifhe drives, he has a probability of 0.1 of being late. If he walks, his probability of being late rises to 0.25. Let W = Walk, D = Drive, L = Late, and NL = Not Late. Which of the following tree diagrams summarizes
A
Use Scenario 4-7. The weight of the pigs after four weeks is
B. the response variable.
Use Scenario 6-10. Here's Albert's game: You give him $10 each time you roll, and he pays you (in dollars) the amount that comes up on the dice. If P = the amount of money you gain each time you roll, the mean and standard deviation of P are:
C. UP-1,6 and Op-1.2
70. A company produces packets of soap powder labeled "Giant Size 32 Ounces." The actual weight of soap powder in a box has a Normal distribution with a mean of 33 oz. and a standard deviation of 0.8 oz. What proportion of packets are underweight (i.e., weigh less than 32 oz.)? a. 0.106. b. 0.115. c. 0.159. d. 0.212. e. 0.841
a. 0.106.
A consumer group surveyed the prices for a certain item in five different stores, and reported the average price as $15. We visited four of the five stores, and found the prices to be $10, $15, $15, and $25. Assuming that the consumer group is correct, what is the price of the item at the store that we did not visit? a. $5 b. $10 c. $15 d. $20 e. $25
b. $10
Suppose X is a continuous random variable taking values between 0 and 2 and having the probability density function below. ____ 63. Use Scenario 6-7. P(1 X 2) has value a. 0.50. b. 0.33. c. 0.25. d. 0.00. e. none of these.
c. 0.25.
If you draw an M&M candy at random from a bag of the candies, the candy you draw will have one of six colors. The probability of drawing each color depends on the proportion of each color among all candies made. The table below gives the probability that a randomly chosen M&M had each color before blue M & M's replaced tan in 1995.
C. 0.2
The scatter plot below describes the relationship between heights of 36 students and the number of words they spelled correctly in a spelling bee. The closed circles represent first graders and the open circles represent fifth graders. Which of the following statements is supported by the information in the scatter plot? a. The tallest first grader is taller than six of the third graders. b. When the data for first and fifth grades is combined, there is a moderately strong positive relationship between height and how many words were spelled correctly. c. Within each of the two grades, there is a strong negative relationship between height and how many words were spelled correctly. d. The tallest first grader spelled more words correctly than five of the fifth graders. e. All of the fifth graders spelled more words correctly than any of the first graders.
b. When the data for first and fifth grades is combined, there is a moderately strong positive relationship between height and how many words were spelled correctly
You are told that your score on an exam is at the 85 percentile of the distribution of scores. Which of the following is a correct interpretation of this information? a. Your score was lower than approximately 85% of the people who took this exam. b. Your score was higher than approximately 85% of the people who took this exam. c. You answered 85% of the questions correctly. d. If you took this test (or one like it) again, you would score as well as you did this time 85% of the time. e. 85% of the people who took this test earned the same score you did.
b. Your score was higher than approximately 85% of the people who took this exam.
56. Use Scenario 6-12. The distribution of X = the number of questions the student will get correct, is a. binomial with parameters n = 5 and p = 0.2. b. binomial with parameters n = 20 and p = 0.25. c. binomial with parameters n = 5 and p = 0.25. d. binomial with parameters n = 4 and p = 0.25. e. none of these.
b. binomial with parameters n = 20 and p = 0.25.
A marine biologist wants to estimate the mean size of the barnacle Semibalanus balnoides on a stretch of rocky shoreline. To do so, he randomly selected twenty 10-cm. square plots and measured the size of every barnacle in each plot. This is an example of a. convenience sampling. d. simple random sampling. b. cluster sampling. e. multistage sampling. c. stratified random sampling.
b. cluster sampling.
In a particular game, a fair die is tossed. If the number of spots showing is either 4 or 5 you win $1, if the number of spots showing is 6 you win $4, and if the number of spots showing is 1, 2, or 3 you win nothing. Let X be the amount that you win. ____ 93. Use Scenario 6-2. Which of the following is the expected value of X? a. $0.00 b. $1.00 c. $2.50 d. $4.00 e. $6.00
b.$1.00
A simple random sample of size n is defined to be a. a sample of size n chosen in such a way that every unit in the population has the same chance of being selected. b. a sample of size n chosen in such a way that every unit in the population has a known nonzero chance of being selected. c. a sample of size n chosen in such a way that every set of n units in the population has an equal chance to be the sample actually selected. d. a sample of size n chosen in such a way that each selection is made independent of every other selection. e. all of the above. They are essentially identical definitions.
c. a sample of size n chosen in such a way that every set of n units in the population has an equal chance to be the sample actually selected.
The binomial 2C8 expression gives the probability of a. at least 2 successes in 8 trials if the probability of success in one trial is 1/3. b. at least 2 successes in 8 trials if the probability of success in one trial is 2/3. c. exactly 2 successes in 8 trials if the probability of success in one trial is 1/3. d. exactly 2 successes in 8 trials if the probability of success in one trial is 2/3. e. at least 6 successes in 8 trials if the probability of success in one trial is 2/3.
c. exactly 2 successes in 8 trials if the probability of success in one trial is 1/3.
Consider the following scatterplot, which describes the relationship between stopping distance (in feet) and air temperature (in degrees Centigrade) for a certain 2,000-pound car travelling 40 mph. ____ 75. Use Scenario 3-3. If the stopping distance were measured in meters rather than feet (1 meter = approx. 3.28 feet), how would the correlation r change? a. r would be smaller, since the same distances are smaller when measured in meters. b. r would be larger, since the same distances are smaller when measured in meters. c. r would not change, since the calculation of r does not depend on the units used. d. r would not change, because only changes in the units of the x-variable (temperature, in this case) can influence the value of r. e. r could be larger or smaller—we can't tell without recalculating correlation.
c. r would not change, since the calculation of r does not depend on the units used.
We divide the class into two groups: first year students and others. We then take random samples from each group. This is an example of
d. stratified random sampling
